1. Field of the Invention
This invention relates to an improvement in a paper feeder of, for example, an electrophotographic reproducing machine, and more particularly to a universal paper feed cassette capable of housing recording paper of different sizes as required.
2. Description of the Prior Art
As is well known, an electrophotographic reproducing machine is provided with a paper feeder, the construction of which is as shown in FIG. 1. In such a paper feeder, a spring lift member F which forces up a bottom plate D, on which recording paper C is placed, of a paper feed cassette A toward a paper feed unit E is provided on a paper feed base B, onto which the paper feed cassette A can be attached.
It is necessary in a paper feeder with the above construction that the contact pressure X between the recording paper C and a belt e in the paper feed unit E is maintained at a substantially constant level. The spring lift member F usually receives the spring force of a spring (not shown). Accordingly, only when a special cassette housing recording paper of a predetermined size is used, the contact pressure X, the value of which is proportional to the weight of the recording paper, can be applied thereto. However, when a universal paper feed cassette housing recording paper of various sizes is used, a contact pressure proportional to the weight of the recording paper cannot be obtained since the weight of one size of recording paper stacked to a certain thickness may be several times that of another size of recording paper stacked to the same thickness.